idk, I might consider my self slightly biased because I like the fly.io team, but fly.io has a really simple story for deploying docker images. It'll build them for you, host them, give you secure ssh access, handle connecting to other instances via nice "friendly" names...

I ran several things in Heroku and besides having a point-and-click Postgres product and add-ons Fly can run your app pretty easily. Unless those are the things which you mean that make Heroku super simple.

The automated ssl cert generation is pretty cool. Although certbot works just as well honestly. I'm going to give fly.io a try soon.